Summary The pilot/owner of the Skyhopper aircraft went to the Smiths Falls airport to work on his aircraft about noon on the day of the occurrence. When he arrived at the airport, he stopped to talk to a friend and then went to his own hangar where the Skyhopper was stored. Around 1300 eastern daylight time the friend heard and observed the Skyhopper taxi past his hangar, but did not see or hear the aircraft take off. The aircraft would have departed from a 4 000 by 75 foot east/west oriented asphalt runway. Around 1400, a witness heard an unusual sound coming from the aircraft and then heard the aircraft engine sputtering. When she looked up, she observed that the right wing had separated from the aircraft, and the aircraft was descending out of control. It struck the ground less than a mile from the witness, fatally injuring the pilot/owner. The accident occurred during the hours of daylight in good visual meteorological flight conditions with light wind. Ce rapport est galement disponible en franais. Other Factual Information The pilot was issued his private pilot licence in 1958, commercial pilot licence in 1962, and airline transport pilot licence in 1968. According to entries in his pilot log book, most recent being 03 January 1998, he had flown a total of 7 556 hours. He was certified and qualified for the flight in accordance with existing regulations. Although never certified as an aircraft maintenance engineer, he served in the military as an aircraft airframe technician and had extensive experience as an aircraft maintenance engineer apprentice, carrying out maintenance on civilian aircraft. The aircraft was an amateur-built, single-place, low-wing, tail-wheel type aircraft. It had a maximum gross weight of 1 300 pounds and was powered by a 108 horsepower Lycoming model O-235 engine. The wings were of wood construction, fabric- covered, with a metal-covered leading edge. Overall wing span was 26 feet. Construction of the aircraft was completed in 1962. According to the most recent entry in the aircraft journey log, 09 April 1998, it had been operated a total of 756 hours flying time. Work reports on file indicate the wings were inspected and re-covered in June 1979. The pilot purchased the aircraft in August 1996 and according to log book entries had flown it a total of 35 hours since that date. Figure 1 - Separated section of right wing The main wreckage was located two miles south of the airport and the separated section of the right wing was 3 000 feet north of the main wreckage, resting above the ground in brush type trees. The right wing main spar separated from the aircraft 97 inches in from the wing tip, and the rear spar separated 56 inches in from the wing tip. The front spar had fractured in one location and the rear spar in three locations. There was no sign of rubbing on the surfaces of any of the spar fractures. The bottom surface of the trailing edge of the right wing tip was ground down through two layers of wood. The ground-off surface had a fresh appearance and was free of dirt or debris. Figure 2 - Scraped mark on bottom of right wing tip There were no marks on the runway that were associated with any abnormal operation of the Skyhopper aircraft. It is not known if the pilot operated the aircraft from any other aerodrome that day. The pilot's friend stated that the occurrence pilot had flown the Skyhopper in company with the friend's aircraft on the weekend prior to the accident. The friend reported that, to his knowledge, there were no abnormalities with the operation of the Skyhopper on that occasion. A load and stress analysis of the two wing spars revealed they had a positive margin of safety when exposed to a 3.8 g load factor and a factor of safety of 1.5. It was also calculated that the main (front) spar had the lowest margin of safety and in the event of an overstress, it would be expected to fail before the rear spar. The wing had been constructed with wood of aircraft specification and quality. There was no sign of damage to the wood from decay or insect attack that would contribute to the cause of the wing failure. It was not possible to determine whether the wood had been damaged prior to the accident either by static overload or progressive fatigue nor was it possible to quantify the force that would have been applied to the wing spars associated with the ground-off portion of the lower rear corner of the right wing tip.